SAFETY IN THE PLANT
MANAGING DOCUMENTATION From a legislative viewpoint, the most important aspect is to maintain all explosion prevention documentation, highlighting the steps and mitigations that were (or were not) taken, should an incident occur.
An assessment involves classifying the
factory into zones, differentiating between gas or dust explosion risks and their potential likelihood. Harmonised standards from the EN60079 series outline this classification, ranging from No Risk where there is no potential gas or dust atmosphere in the factory, through Zone 22 (or Zone 2 for gas) where the risk may be present for up to 10 hours per year, Zone 21 (Zone 1 for gas) where there is danger for up to 1,000 hours per year, and finally, Zone 20 (Zone 0 for gas) where there is frequent or continuous risk. Bear in mind that any major changes or new processes – perhaps as a result of increased production rates or advancements in technology – will require a new explosion protection document, so identifying any future plans for remodelling or expansion will be extremely worthwhile.
Fig. 1. Example of a zoning dust collector
Should process changes lead to the need for a different ATEX certification, equipment can be modified but will need recertification from a notified body or expert to ensure CE conformity.
CONSTRUCTOR’S CHALLENGE A prime example of Zone 20 would be the constant dust cloud inside a dust collector (see Fig. 1). Tis highlights the importance of ensuring that any such equipment – including protective systems such as isolation devices, safety devices such as overload protection devices, or components such as vent ducts – is fully compliant with ATEX 114 Directive 2014/34/EU (formerly ATEX 95). By compelling constructors to carry out
Donaldson dust collector successfully handles
combustible dust explosion during independent field test
an Ignition Hazard Analysis, evaluating the risk level of hot surfaces, flames and hot gasses, mechanically generated sparks and static electricity, etc., end-users can rest assured that the equipment they install is not a potential ignition source. In legislative terms, there is again a distinction made in terms of dust zoning and gas zoning, as well as underground (Group I) and above-ground (Group II) equipment. As a leading manufacturer of Group II equipment, Donaldson can self-declare equipment providing the lowest (Normal) level of protection for gas and dust (3G or 3D), as well as for non-electrical aspects of the High (2G or 2D) level equipment. A notified body is responsible for approval of its electrical systems, however, and for all aspects of the top level of protection. Tis Very High (1G or 1D) category ensures that no ignition source is present during normal
operation, as well as in the event of malfunctions.
And it is at this point where the two
ATEX directives intertwine, with the specific level of protection required for operation in a previously specified zone now becoming apparent. So, for example, Zone 22, the lowest dust danger zone, will require 3D-level equipment, while 1D protection will be needed in Zone 20. Manufacturers, of course, are also obliged to supply equipment with the correct markings and provide clear information on any residual risks, safe use and any limits. Conforming equipment will clearly display ATEX identification in the form of the hexagon, followed by numbers stating the equipment group (e.g. II for above ground) and the safety category (e.g. 1 for Zone 20/0), plus the letter D or G to signify the type of explosive atmosphere. Te next two sets of markings verify the dust group (combustible, conductive or non- conductive) and temperature class. When it comes to hazardous and combustible dust, Donaldson helps its clients develop a risk-mitigation solution that meets their unique needs. From the initial site visit and process audit to installation and compliance support, the company helps ensure its customers have the right solution in place.
Melina Diaz is product engineering manager at Donaldson.
donaldson.com/combustible-dust
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